Thread subject: Diptera.info :: Late autumn Sphaeroceridae, Oct.28, 2006

Posted by Dmitry Gavryushin on 30-10-2006 14:34
#1
I took a walk in a forest last Saturday and saw a lot of small dark flies gliding on water surface of a small pool (actually it was a car track filled with water) on the edge of a mixed forest. It was around 5 degrees or even less, but they were quite active. I collected some using a film box, thinking it's Ephydridae. But when I took some pictures at home I understood they were Shaeroceridae, size 1.5 to 2mm. I've contacted Dr. Roh?ček on this matter, and here's his comment:

Yes, I know this species imitating Ephydridae very well and I also observed it running on water surface (most often in autumn). It is Pseudocollinella humida (Haliday, 1836), a common species associated with muddy shores of waters but often found also along small creeks on gravel dirted by mud etc. In contrast to Leptocera and Rachispoda it only has 4 (2 pairs) scutellars, 1 pair of strong acrostichals, and less rich mid tibial chaetotaxy. The female can be easily recognized by strong blunt spine-like seta on apex of cercus.

Posted by Nikita Vikhrev on 30-10-2006 15:18
#2
Dima, next step is to persuade Dr. Rohachek to registrate as a new member of Diptera.info. Do it, please!

Posted by Dmitry Gavryushin on 30-10-2006 15:40
#3
Well I'd love to if I only could... ;) We all need even more interesting posts to allure more experts... or become experts ourselves :)

Posted by Kahis on 30-10-2006 17:24
#4
I'd say Pseudocollinella humida, but who knows what Russian species may look similar. Well, Dr. Rohachek obviously does, so you'd better ask him :)
Edited by Kahis on 30-10-2006 17:24

Posted by Kahis on 30-10-2006 17:28
#5
Features to look for in this case are: Only 4 major setae of scutellum, no hairs; two strong presutural acrostichal setae; middle basitarsus (1st segment of 2nd tarsus) with a strong seta on lower side - poorly visible in the photo but I think it's there; whitish dusting on face; mid tibiae without very long setae.

It does help to know that this species is very common on small patches of mud, together with the ephydrid Scatella and a few species of the spaherocerids Rachispoda and Leptocera.
Edited by Kahis on 30-10-2006 17:31